Cerebral hypoxia during labor represents a risk factor for death or severe neurologic complications (e.g., cerebral palsy). At present, there are no commercially available monitors that can be used to detect cerebral hypoxia, other than fetal heart rate (FHR) monitors that use changes in basal heart rate and changes in FHR variability and timing of FHR decelerations to indirectly assess fetal asphyxia. Although fetal heart rate monitoring provides important information regarding fetal oxygenation, this information is somewhat limited and provides no information regarding the risk of cerebral palsy. As a consequence, many cesarean sections are performed as a defensive measure to reduce the risk of intrapartum fetal asphyxia by reducing the duration of labor. Unfortunately, defensive cesarean sections entail added maternal risk. Maternal death rates are 21% higher in states with cesarean section rates exceeding 33% than those with rates less than 33%.
In view of the limited information provided by FHR and the risks associated with cesarean procedures, it can be appreciated that it would be desirable to have a more direct way of measuring fetal cerebral oxygenation (i.e., hemoglobin saturation).
References that may be of interest include: U.S. Pat. Nos. 4,537,197, 5,088,493, 5,099,842, 5,228,440, 5,348,002, 5,377,673, 5,823,952, 5,840,023, 5,941,821, 6,049,728, 6,381,480, 6,553,242, 6,594,515, 6,463,311, 6,466,806, 6,484,044, 6,567,678, 6,751,490, 6,846,288, 7,164,938, 7,322,972, 7,515,948, 7,747,301, 7,916,283, 8,121,663, 8,280,469, 8,332,006, 8,423,111, 8,501,099, 8,781,548, 8,852,095, 8,864,667, 8,885,155, 8,930,145, and 8,934,953; U.S. Publication Nos. 2006/100530, 2006/184042, 2007/015992, 2009/069652, 2009/108205, 2010/081904, 2011/239766, 2013/112001, 2013/190589, 2013/324815, 2014/142404, 2014/275943, 2014/343384, 2014/378811, 2015/051473, and 2015/099973; German Patent Publication No. DE 4400674 A1; and, “Noninvasive monitoring of cerebral blood oxygenation in ovine superior sagittal sinus with novel multi-wavelength optoacoustic system” to Petrova et al. (27 Apr. 2009/Vol. 17, No. 9/OPTICS EXPRESS 7285).